Detection of an electron paramagnetic resonance signal in the S0 state of the manganese complex of photosystem II from Synechococcus elongatus

The Mn(4)-cluster of photosystem II (PSII) from Synechococcus elongatus was studied by electron paramagnetic resonance (EPR) spectroscopy after a series of saturating laser flashes given in the presence of either methanol or ethanol. Results were compared to those obtained in similar experiments done on PSII isolated from plants. The flash-dependent changes in amplitude of the EPR multiline signals were virtually identical in all samples. In agreement with earlier work [Messinger, J., Nugent, J. H. A., and Evans, M. C. W. (1997) Biochemistry 36, 11055-11060; Ahrling, K. A., Peterson, S., and Styring, S. (1997) Biochemistry 36, 13148-13152], detection of an EPR multiline signal from the S(0) state in PSII from plants was only possible with methanol present. In PSII from S. elongatus, it is shown that the S(0) state exhibits an EPR multiline signal in the absence of methanol (however, ethanol was present as a solvent for the artificial electron acceptor). The hyperfine lines are better resolved when methanol is present. The S(0) multiline signals detected in plant PSII and in S. elongatus were similar but not identical. Unlike the situation seen in plant PSII, the S(2) state in S. elongatus is not affected by the addition of methanol in that (i) the S(2) multiline EPR signal is not modified by methanol and (ii) the spin state of the S(2) state is affected by infrared light when methanol is present. It is also shown that the magnetic relaxation properties of an oxidized low-spin heme, attributed to cytochrome c(550), vary with the S states. This heme then is in the magnetic environment of the Mn(4) cluster.

[Vascular effects of gestagens--biochemistry versus epidemiology]

The available epidemiologic data indicate that the sequential addition of progestogens enhances the protective effect of estrogens on the cardiovascular risk. A considerable decrease in LDL-cholesterol is also observed during use of progestogens with androgenic properties. The estrogen-dependent reduction of LDL oxidation is not impaired by progestogens. While estrogens inhibit the endothelial synthesis of adhesion molecules, the activation of monocytes and platelets and the proliferation and migration of smooth muscle cells, the effect of progestogens is rarely investigated. A vasoconstrictory effect of progestogens which may attenuate the estrogen-induced dilation of arteries, was not observed in all clinical investigations. It is presumably based on a reduction of estrogen-stimulated release of nitric oxide by progestogens. In most animal experiments, a progestogen-induced enhancement of contractility of arteries was measured, too. A relaxing effect of progesterone was found in in vitro-experiments, while the results on endothelium-independent effects of synthetic progestogens were contradictory. The sex steroids influence the structure of the vessel wall, whereby the elasticity of arteries is enhanced by estrogens and reduced by progestogens. Oral contraceptives may increase the distensibility of veins which correlates with the hormonal potency of the progestogen. During hormone replacement therapy, venous distensibility is also increased which is mainly due to the action of the estrogen. In vitro experiments with veins revealed a dilatory effect of progestogens. With regard to possible unfavourable effects of progestogens on the vessel wall it is recommended to use the additional progestogen at the minimal effective dose necessary for prevention of endometrial hyperplasia.

Effect of two oral contraceptives containing ethinyl estradiol and gestodene or norgestimate on different lipid and lipoprotein parameters

The effect of a triphasic oral contraceptive containing ethinyl estradiol and gestodene (EE/GSD) on various lipid and lipoprotein parameters was compared with that of a monophasic formulation containing 35 micrograms ethinyl estradiol and 250 micrograms norgestimate (EE/NGM). Blood samples were collected from 46 women on days 2, 11, and 21 of the preceding control cycle and of the third, sixth, and twelfth treatment cycles. There was no significant difference between formulations with regard to the influence on any measured parameter. As compared with controls, a significant increase was observed in the plasma levels of total triglycerides (24-78%), total phospholipids (7-20%), very low density lipoprotein (VLDL) triglycerides (61-76%), VLDL-phospholipids (14-60%), low density lipoprotein (LDL) triglycerides (8-35%), LDL-phospholipids (28-30%), high density lipoprotein (HDL) cholesterol (8-16%), HDL 3-cholesterol (11-20%), HDL-triglycerides (17-66%), HDL-phospholipids, HDL 3-phospholipids (7-11%), apolipoprotein (apo) A-I (5-20%) and apo A-II (10-40%) during treatment with both formulations. In contrast, the LDL-cholesterol levels were significantly decreased. These changes in lipid metabolism appear to reflect a predominance of the effect of the estrogen component. The results indicate that both low dose oral contraceptives containing different progestins and different amounts of EE do not exert a deleterious effect on lipoprotein metabolism, as high HDL-cholesterol and low LDL-cholesterol levels are known as low risk factors of cardiovascular disease. In contrast to endogenous hypertriglyceridemia, an EE-induced rise in triglyceride levels does not appear to increase cardiovascular risk if LDL is not increased.

A randomized cross-over study on various hormonal parameters of two triphasic oral contraceptives

The effect of two triphasic oral contraceptives (Triquilar [TRQ] and Trisiston [TRS]) containing ethinyl estradiol (EE) and levonorgestrel (LNG) on various hormonal parameters was investigated in 26 women during a cross-over study. TRS consisted of 0.03 mg EE + 0.05 mg LNG (six tablets), 0.04 mg EE + 0.075 mg LNG (six tablets), and 0.03 mg EE + 0.15 mg LNG (nine tablets), whereas TRQ was different in the second phase (five tablets) and third phase (10 tablets). Blood samples were taken on days 6, 11, 21, and 28 of the control and washout cycles and the third treatment cycle. Both formulations inhibited ovulation reliably and decreased the serum levels of gonadotropins, free testosterone, and dehydroepiandosterone sulfate in a time-dependent manner, whereas estradiol and testosterone were already suppressed on day 6, indicating a direct suppressive effect on ovarian steroid synthesis. Prolactin, which rose sporadically in some women, was not significantly changed. In contrast, the levels of sex hormone binding globulin, corticosteroid binding globulin, and cortisol were significantly elevated by 100%. During the hormone-free interval of 7 days, all parameters returned at least partly to baseline. There was no significant difference between the effects of both formulations. The results suggest the possibility of a direct inhibitory effect of contraceptive steroids on ovarian steroid synthesis.

Effect of near-infrared light on the S2-state of the manganese complex of photosystem II from Synechococcus elongatus

The Mn cluster of Photosystem II (PSII) from Synechococcus elongatus was studied using EPR. A signal with features between g = 5 and g = 9 is reported from the S2-state. The signal is attributed to the manganese cluster in a state with a spin 5/2 state. Spectral simulations of the signal indicate zero field splitting parameters where the |E/D| was 0.13. The new signal is formed by irradiating PSII samples which contain the spin = 1/2 S2-state using 813 nm light below 200 K. This effect is attributed to a spin-state change in the manganese cluster due to absorption of the IR light by the Mn-cluster itself. The signal is similar to that reported recently in PSII of plants [Boussac, A., Un, S., Horner, O., and Rutherford, A. W. (1998) Biochemistry 37, 4001-4007]. In plant PSII the comparable signal is formed at a lower temperature (optimally below 77 K), and gradual warming of the sample in the dark leads to the formation of the state responsible for the well-known g = 4.1 signal prior to formation of the spin 1/2 multiline signal. In the present work using cyanobacterial PSII, warming of the sample in the dark leads to the formation of the spin 1/2 multiline signal without formation of the g = 4 type signal as an intermediate. These observations provide a partial explanation for the long-standing "mystery of the missing g = 4 state" in cyanobacterial PSII. The observations are rationalized in terms of three possible states which can exist for S2: (i) the spin 1/2 multiline signal, (ii) the state responsible for the g = 4.1 signal, and (iii) the new spin 5/2 state. The relative stability of these states differs between plants and cyanobacteria.

Plasma profiles of transdermal 17 beta-estradiol delivered by two different matrix patches. A four-way cross-over study in postmenopausal women

The aim of this study was to investigate the systemic bioavailability and plasma profiles of 17 beta-estradiol (CAS 50-28-2, E2) after the application of two types of matrix patches for the transdermal delivery of E2: MenorestTM (the test patch) with delivery rates of 37.5, 50 and 75 micrograms E2/day and a reference patch with a delivery rate of 50 micrograms E2/day. All 3 test patches were identical in composition, achieving different transdermal E2 delivery rates by variations in the surface area (11.0, 14.5 and 22.5 cm2). All 4 patches were each worn by 24 postmenopausal women over a 4-day period (i.e. 96 h), each of the 4 treatment periods being separated by a 7-day wash-out period according to a randomized, 4-way crossover design. Blood samples were collected before and 3, 6, 9, 12, 24, 34, 48, 58, 72, 84, and 96 h after each patch application. Plasma E2 concentrations were determined by a specific direct radioimmunoassay method. The following pharmacokinetic parameters were evaluated: AUC0-96h; Cmax, tmax, Cmin, Caverage. The course of the E2 plasma levels over the total test period (96 h) was relatively constant for all patches. For the test patch, a linear relationship between the pharmacokinetic parameters and the different patch areas (i.e. dosages of 37.5, 50, 75 micrograms E2/d) could be shown (correlation coefficient 0.99). The resulting Cmax values for the patch were: 44.2, 58.3, and 92.1 pg E2/ml, corresponding to Caverage values of 39.5, 45.5, and 70.6 pg E2/ml. The reference patch and the test patch, at a dose of 50 micrograms E2/d, were similar in terms of Cmax, while the Caverage, AUC0-96h and Cmin were significantly higher with the test patch. The systemic bioavailability of the reference patch was comparable to that of the test patch at a dose of 37.5 micrograms E2/d: AUC0-->96h 3017.5 +/- 1312.4 pg/ml.h for the reference patch and 3375.9 +/- 1254.7 pg/ml.h for the test patch. A physical model for the calculation of the course of the E2 levels was used to describe the experimentally determined data. However, in the evening, periodically higher E2 plasma levels were observed for all patches than in the morning. From these results it can be concluded that E2 plasma profiles produced by the test patch are reproducible, and in the physiological range consistent with the early to mid follicular level in the premenopausal woman over 4 days (96 h), correlating with the doses administered (37.5-50-75 micrograms E2/d). Additionally, the systemic bioavailability of the test patch at a dose of 37.5 micrograms E2/d is comparable to that of the reference patch at a dose of 50 micrograms E2/d.

Mammary derived growth inhibitor is not a distinct protein but a mix of heart-type and adipocyte-type fatty acid-binding protein

The amino acid sequence of the mammary derived growth inhibitor (MDGI) from bovine mammary gland (Böhmer, F.-D., Kraft, R., Otto, A. , Wernstedt, C., Hellman, U., Kurtz, A., Müller, T., Rohde, K., Etzold, G., Lehmann, W., Langen, P., Heldin, C.-H., and Grosse, R. (1987) J. Biol. Chem. 262, 15137-15143) revealed 95% identity to bovine heart fatty acid-binding protein (H-FABP), explaining the observed immunocross-reactivity. However, a cDNA encoding MDGI has not been found to date. Artificial MDGI cDNA was expressed in an in vitro transcription/translation assay. Analysis by isoelectric focusing of the immunoprecipitated in vitro translation products of lactating bovine mammary gland mRNA did not indicate a protein corresponding to the in vitro translation product of artificial MDGI mRNA. Moreover, two-dimensional electrophoresis of bovine mammary gland proteins confirmed the absence of a protein with the pI of the in vitro translated artificial MDGI mRNA in bovine mammary gland and instead revealed, apart from H-FABP, an unknown protein that was recognized by anti-H-FABP antibodies. From lactating bovine mammary gland the cDNA for adipocyte fatty acid-binding protein (A-FABP) was cloned. The in vitro translation of recombinant mRNA derived from this cDNA yielded a polypeptide that behaved like the unknown immunoreactive protein. Western blotting and immunofluorescence using monospecific antibodies demonstrated the coexistence of H-FABP and A-FABP in the lactating mammary gland. Taking into account that deviations of the MDGI sequence from the bovine H-FABP sequence correspond with A-FABP we attribute the structure originally reported as MDGI to a mix of these proteins.

Effects of progestogens on haemostasis

Epidemiological data suggested an involvement of the progestogen component in the pathomechanism of venous and arterial diseases during intake of oral contraceptives. The influence of progestogens on haemostasis parameters depend on type and dose of the progestogen, the presence of an estrogen, the route of application, and the duration of use. Treatment of women with progestogen-only preparations caused only minor effects on coagulation and fibrinolysis. Similarly, during hormone replacement therapy with natural estrogens, the additional application of progestogens induced no unfavourable changes on haemostasis. In contrast, the use of ovulation inhibitors resulted in an acceleration of coagulation and fibrinolysis. This is primarily induced by the marked action of ethinylestradiol on hepatic and vascular function. Progestogens with androgenic properties may counteract the estrogen-induced changes in the hepatic synthesis of platelet aggregation and readiness for coagulation. Estrogen and progesterone receptors are localized in endothelial and smooth muscle cells of the vessel wall, but there are differences in the response of veins and arteries to sex steroids. Estrogens and progestogens may influence collagen and elastin synthesis, and the release of vasoactive compounds and of factors controlling fibrinolysis from endothelium. In veins, progestogens may increase distensibility and capacitance resulting in a decreased blood flow. In predisposed women, this may lead to venous stasis and thrombosis. In arteries, progestogens may act as vasoconstrictors, and may enhance vasospasms at sites of injured endothelium which finally may lead to ischemic diseases.

Comparative pharmacology of newer progestogens

The newer progestogens desogestrel, norgestimate, gestodene, dienogest and nomegestrol share the common property of having weak or no androgenic effects, but there is great variation between agents in their pharmacokinetic properties and hormonal activities. Both desogestrel (acting as 3-keto-desogestrel) and norgestimate (acting mainly through levonorgestrel) are prodrugs. While nomegestrol is derived from 19-norprogesterone, the other compounds are 19-nortestosterone derivatives: desogestrel, norgestimate and gestodene belong to the subgroup of 13-ethyl-gonanes with an ethinyl group at C17 alpha, and dienogest represents an estrane (13-methyl-gonane) with a cyanomethyl group at C17 alpha. Both dienogest and nomegestrol have antiandrogenic properties. In proportion to the dose, the highest serum concentrations are observed after intake of gestodene. When combined with ethinylestradiol, gestodene and 3-keto-desogestrel accumulate in serum during daily treatment because of slowed-down elimination. This is probably caused both by binding to sex hormone-binding globulin (SHBG) and by inhibition of inactivating enzymes. Dienogest does not accumulate in serum, although at a dose of 2 mg very high serum concentrations of dienogest are reached. The most potent progestogens are gestodene and desogestrel, while the effect of dienogest and nomegestrol on endometrium and cervix is less, even though in a similar range. As the ovulation-inhibiting effect is brought about not only by receptor-mediated interactions but also by a direct inhibition of steroid biosynthesis, dienogest and nomegestrol are much less effective than gestodene, desogestrel and norgestimate. Ethinylated progestogens, particularly gestodene, have been demonstrated to inhibit cytochrome P450 enzymes. Both gestodene and desogestrel may moderately reduce SHBG levels and counteract the stimulating effect of ethinylestradiol on hepatic serum proteins, while dienogest and nomegestrol have no influence. Compared with progestogens with androgenic properties which may restrict the stimulatory action of ethinylestradiol on haemostatic parameters, the newer progestogens do not seem to be superior with respect to haemostasis. There are no data on the direct effect of the compounds on the arterial and venous vessel wall. Due to the less pronounced antagonism on ethinylestradiol-induced changes in lipid metabolism, the newer progestogens appear to be beneficial rather than deleterious, although atherosclerosis was probably not promoted by the older formulations because of the direct effect of ethinylestradiol on the arterial wall. There is no evidence for a lesser impact of the newer progestogens on carbohydrate metabolism, which is mostly impaired by the estrogen component in oral contraceptives. Formulations containing the newer progestogens are, however, preferable in patients with hyperandrogenaemia, the symptoms of which may be improved by the suppression of total and free testosterone and an increase in SHBG; an additional beneficial effect of the antiandrogenic properties of dienogest or nomegestrol remains to be proven.

[Significance of hereditary thrombophilia for risk of thrombosis with oral contraceptives]

Oral contraceptives increase the natural incidence of venous thromboses of 1-2/10,000 women per year 3-to 4fold. Recent investigations have shown that during intake of desogestrel or gestodene containing formulations the risk is twice that with older low-dose ovulation inhibitors. This difference is larger in first time users than in women who had previously used an oral contraceptive. During pregnancy, the incidence of thromboses rises up to 10/10,000 women-years and post partum up to 40/10,000 women-years. In about 60 % of thromboses no causal explanation can be found. It is suggested that in 40 % of all cases an inherited thrombophilia is present. Among the hereditary types of thrombophilia, the resistance against activated protein C (APC-resistance) represents nearly 50 %, while altogether 15 to 20 % is based on a deficiency of antithrombin III, protein C or protein S. APC-resistance the prevalence of which is 3-5 % in the general population, increases the risk of thrombosis 8fold and in users of oral contraceptives 35fold. Protein C-deficiency (prevalence 0.1-0.5 %) increases the risk of thrombosis 9fold and in users of oral contraceptives 15fold, while antithrombin III-deficiency (prevalence 0.02-0.05 %) enhances the risk in pill-users 8fold. Ovulation inhibitors do not influence risk of thrombosis in women with protein S-deficiency. Antiphospholipid-antibodies the concentration of which may increase during treatment with oral contraceptives, represent a considerably enhanced risk of thrombosis, too. A positive family history (before age of 40 years) indicates an inherent thrombophilia. In these risk groups, the cost/benefit ratio of a selective screening is unfavorable, as at most 70 % of the hereditary thrombophilias can be diagnosed by laboratory analysis, and only very few patients will actually experience a thrombotic event: only 3 of 1000 carriers of APC-resistance will suffer from thrombosis during oral contraception per year. On the other hand, a negative result of laboratory tests does not exclude a hereditary thrombophilic disorder which as yet cannot be substantiated. It is not yet clarified whether a selective screening is superior to a careful assessment of individual and family history. A general screening cannot be justified because of the unfavorable cost/benefit ratio. If the individual or family history or pathological laboratory parameters indicate an enhanced risk of thrombosis, this risk has to be carefully weighed against the consequences of discontinuation of pill use. Those few individuals with risk factors who will experience a thrombosis, cannot be identified in advance. If in patients with thrombophilic disorders and/or other risk factors the use of oral contraceptives represents a particularly high risk, other contraceptive methods should be taken into consideration. If a patient with risk factors decides for the use of oral contraceptives, she has to be informed that in the case of symptoms indicating a thrombosis, the physician has to be consulted immediately. The earlier an appropriate therapy is initiated, the more effectively an acute pulmonary emboli or permanent damages, e.g. the post-thrombotic syndrome, can be prevented.

Gestodene-containing contraceptives

As GSD is the most potent progestogen used in oral contraceptives, the doses of GSD can be lower than those of other progestogen components. The monophasic (30 micrograms EE + 75 micrograms GSD) and the triphasic formulation (30 micrograms EE + 50 micrograms GSD/40 micrograms EE + 70 micrograms GSD/30 micrograms EE + 100 micrograms GSD) suppress gonadotropin release and ovarian function profoundly and inhibit ovulation reliably. The strong anti-estrogenic and progestogenic effectiveness of GSD is based on the high GSD serum concentrations achieved during daily intake. Because of the weak androgenic properties of GSD, both formulations can be characterized as estrogen-dominant with respect to their hepatic effects. Except for the first cycles, both formulations afford good cycle control, and the rate of side effects is similar to that with comparable low-dose oral contraceptives. The levels of total and free androgens and androgen precursors, as well as of peripheral androgen activity, are significantly reduced, resulting in a reduced incidence of acne. The concentrations of SHBG and other serum-binding globulins are elevated considerably, and thyroid function is almost unaffected. The estrogen-dominant effect on hepatic metabolism of both formulations also is reflected by a significant increase in the levels of triglycerides and VLDL, HDL, and some apolipoproteins, while LDL-CH and total CH remain unchanged. Similar to other low-dose oral contraceptives, the GSD-containing preparations cause a slight impairment of glucose tolerance that does not appear to be of clinical relevance. However, a significant increase exists in pro-coagulatory and fibrinolytic activity that leads to a considerable stimulation of fibrin turnover. In predisposed women, this may contribute to an elevated risk of venous and arterial thromboembolic diseases.

Effect of two oral contraceptives containing ethinylestradiol and gestodene or norgestimate upon androgen parameters and serum binding proteins

The effect of a triphasic oral contraceptive containing ethinylestradiol and gestodene (EE/GSD) on various serum hormonal parameters was compared with that of a monophasic formulation containing 35 micrograms ethinylestradiol and 250 micrograms norgestimate (EE/NGM). Blood samples were collected from 46 women on days 2, 11, and 21 of the preceding control cycle and of the third, sixth and twelfth treatment cycle. There was no significant difference in the influence on any hormonal parameter between both formulations. Both EE/GSD and EE/NGM caused a time-dependent suppression of serum dehydroepiandrosterone sulphate (DHEA-S) by 20-30% (p < 0.01) and a reduction of 5 alpha-androstane-3 alpha, 17 beta-diol glucuronide by 50-60% (p < 0.01) during each treatment cycle, while androstenedione levels were reduced by 25% (p < 0.01). There was also a significant decrease in the levels of total testosterone by 30-35% (p < 0.01) and free testosterone by 60% (p < 0.01), while sex hormone-binding globulin (SHBG) was increased by 200-240% on days 11 and 21 (p < 0.01). During the pill-free interval the SHBG levels were reduced to a certain degree but remained elevated by 100% as compared to the pretreatment values. The serum levels of corticosteroid-binding globulin (CBG) which is known to be influenced only by the estrogenic component of combination pills, increased significantly by 170% (p < 0.01) during each treatment cycle. During the pill-free interval of 7 days, the CBG levels decreased but were still elevated by 90-100% as compared to the control cycle. Similarly, the serum levels of cortisol were significantly elevated by 110-140% (p < 0.01) during treatment with both preparations. The results demonstrate a profound suppression of androgen levels and peripheral androgen metabolism.

Formation of ethinylestradiol in postmenopausal women during continuous treatment with a combination of estradiol, estriol and norethisterone acetate

Previous studies indicated that during treatment of postmenopausal women with preparations containing norethisterone, a small proportion of the progestogen is aromatized into ethinylestradiol. We therefore investigated the serum concentrations of estradiol, ethinylestradiol and norethisterone in 25 patients of a gynecological practice who were continuously treated for climacteric complaints with a combination of 2 mg estradiol, 1 mg estriol and 1 mg norethisterone acetate for a time period between 4 months and 6 years. Blood sampling occurred between 1 and 20 h after intake of the last tablet. The mean serum concentration of estradiol was 138 +/- 50 (53-279) pg/ml, of ethinylestradiol 18.1 +/- 13.5 (0-44) pg/ml, and of norethisterone 5.1 +/- 3.5 (0.7-11.6) ng/ml. The serum concentrations of estradiol showed a broad maximum between 1 and 14 h, and those of norethisterone a steep rise to maximum within 1-4 h after intake followed by a subsequent decline. Contrary to this, the ethinylestradiol levels were not related to the time after application indicating that the aromatization of norethisterone mainly occurs in peripheral tissue. There was no correlation between age, body mass index or duration of treatment and the ethinylestradiol levels. It is concluded that in the presence of the high estradiol concentrations the low conversion rate of norethisterone into ethinylestradiol is probably without clinical significance.